Functionalised Seed Pods for the Sorption of Crystal Violet from Aqueous Solution: Kinetics and Equilibrium Studies

Abstract

The release of dye-containing effluents from several industries into natural
water bodies continues to pose a serious threat to the ecosystem. Even
though several conventional wastewater treatment technologies abound,
their usage in developing nations has been limited due to their high cost.
This has prompted research into the use of low-cost materials, such as
agricultural waste biomass for sequestering such dyes from wastewater.
The ability of CH3COOH-functionalised Millettia thonningii seed pods
(FMTP), an agricultural waste, as an adsorbent for the sequestration of
Crystal Violet (CV) dye from aqueous solutions is investigated in this study.
Fourier Transform Infrared (FTIR) spectroscopy was used to characterize
the functionalized adsorbent and its precursor. The pseudo-first-order,
pseudo-second-order, and Elovich's kinetic models were used to analyze
the kinetic data, while Langmuir and Freundlich isotherm models were used
to analyze the equilibrium data using the non-linear regression method. To
evaluate the adsorption data and identify the best-fitting kinetic and isotherm
models, four error functions were used: Coefficient of Determination (R2
),
Chi-Square (χ
2
), Sum of Error Squares (SSE), and Percent Deviation (% D).
The adsorption kinetics was best described by Elovich's kinetic model, while
the adsorption equilibrium was better described by the Freundlich model,
indicating that the mechanism of adsorption is predominantly chemisorption
onto a heterogeneous adsorbent surface. The maximum adsorption capacity
of the functionalized adsorbent was 34.8270 mg/g as given by the
Langmuir Qmax. Experimental results revealed that acetic acid
functionalized biomass is a suitable adsorbent for removing CV from
aqueous solutions. Its application in the treatment of industrial wastewater
should be investigated further.